People cough in order to clear their airways. Most coughs are caused by viruses and settle down by themselves, but some people develop persistent coughing which can be anywhere from 8 weeks to several years. This is called chronic cough. People with chronic cough find the symptom distressing and it can have a major impact on their quality of life. Patients with chronic cough often report a sensation at the back of their throat which makes them feel an urge to cough. There is some evidence that Lidocaine (an anaesthetic used during medical procedures) can suppress a person's cough when given to patients via a nebuliser (a machine that turns liquid into a fine mist).